This (new) glitch is going on for a while.
"fast move" is a useless glitch, (almost) nobody is using it. I am not sure why people want to enable it, but it is included in some cbug resources.

The only thing that might be handy is by adding some extra info about it on wiki.(to prevent multiply threads about this...) It is in my opinion a bit overdoing to fix a glitch caused by another (useless)glitch, which is disabled by default.

The local player will not see this animation himself, he will be seeing the default animation. But the remote players will see it as the image and video.

Video
A player starts watching over a remote player on 0:07 t/m 0:10. (this is where the 'glitch' is visible)
It is only a petty he didn't film the remote player(as a localPlayer) while he was shooting.

These are both the 'fastmove' bug, initiated in different ways. I don't know yet if they can be seperated.

The fastmove bug was intended to prevent players from 'moving fast' as soon as they stood up and entering aim. When I initially fixed it, it was to prevent people sprinting with heavy weapons whilst aiming. In other words, it was initiated by using the 'sprint' key to stand up from crouching.

This is the same bug, only instead of using the 'sprint' key to stand up, you're using the traditional 'crouch'key. The result is you aren't running with the gun, but instead sliding slightly faster than walking.

Fundamentally it's the same bug. However, from the video it seems one causes desync in crouch states while the other doesn't.

MTA can only tell when a player is fully stood up, and doesn't know when a player starts the process of standing up. Hence, there's a noticable delay in 'standing up' sync because the remote players only get told to start the stand-up process once the local player has fully stood up.

The desync is caused by taking advantage of this delay. Whilst standing up, if a player presses left or right, remotely they will begin doing a crouchroll (because remotely, we dont know they're in the process of standing up). The aiming then takes over as the primary task, but in a bugged-crouched state.